It has been known that organic materials such as thermoplastic resin, thermosetting resin, natural or synthetic rubber, mineral oil, lubricating oil, adhesive, paint, etc. are deteriorated by the action of, for example, heat, oxygen, etc. on production, processing and use, resulting in lowering of the strength of the organic material due to a phenomenon (e.g. molecular cleavage, molecular crosslinking, etc.), change in flow properties, coloring, deterioration of surface physical properties, etc., which results in a decrease in a commercial value. It has hitherto been known that organic materials may be stabilized by containing various phenol and phosphorous antioxidants for the purpose of solving these problems about heat deterioration and oxidation deterioration.
As the phosphorous antioxidant, for example, tris(2,4-di-t-butylphenyl)phosphite is used.
However, these known phosphorous antioxidants had a problem that the stabilizing effect to heat deterioration and oxidation deterioration is insufficient.
On the other hand, as those for solving the problem of the phosphorous antioxidant, there is suggested, for example, a cyclic phosphite having a carbonyloxy alkylene group, such as 2,10-dimethyl-4,8-di-t-butyl-6-{2-3-(3-t-butyl-4-hydroxy-5-methylphenyl)p ropionyloxy!ethoxy}-12H-dibenzod,g!1,3,2!dioxaphosphosine, etc. (JP-A-5-86084).
Although these cyclic phosphite exhibits improved stabilizing effects to heat deterioration and oxidation deterioration, these effects are not fully satisfactory. Accordingly, more efficient antioxidant has been desired.
The present inventors have produced various phosphorous compounds and studied intensively. As a result, it has been found that specific cyclic phosphites having an aminoalkylene or oxyalkylene group in place of a carbonyloxy alkylene group exhibits excellent stabilizing effect. It has also been found that specific cyclic phosphites having an oxyalkylene group in place of a carbonyloxy alkylene group exhibits excellent discoloration-resistant effect. Thus, the present invention has been accomplished.